Patent application title: Legged mobile robot

Abstract:

In a legged mobile robot having an imaging device (such as CCD camera) for
taking an image utilizing incident light from external world in which a
human being to be imaged is present, brightness reduction operation is
executed to reduce brightness of a high-brightness imaging region
produced by high-brightness incident light, when the high-brightness
imaging region is present in the image taken by the imaging device. With
this, when the imaged high-brightness imaging region is present owing to
high-brightness incident light from the sun or the like, the legged
mobile robot can reduce the brightness to image a human being or other
object with suitable brightness.

Claims:

1. A legged mobile robot having an imaging device for taking an image
utilizing incident light from external world in which an object to be
imaged is present, comprising:brightness reduction operation execution
means for determining whether a high-brightness imaging region is present
in the image taken by the imaging device and for executing brightness
reduction operation to reduce brightness of the high-brightness imaging
region produced by high-brightness incident light, when the
high-brightness imaging region is present in the image.

2. The legged mobile robot according to claim 1, further including:a body,
arms connected to the body and hands connected to the arms;and the
brightness reduction operation execution means drives at least one of the
hands to block the high-brightness incident light, thereby reducing the
brightness of the high-brightness imaging region.

3. The legged mobile robot according to claim 2, the object is a human
being, and the brightness reduction operation execution means drives at
least one of the hands to block the high-brightness incident light while
holding imaging parameters of the human being.

4. The legged mobile robot according to claim 1, further including:a body
and a head, which is connected to the body and equipped with the imaging
device;and the brightness reduction operation execution means rotates the
head so as to reduce the brightness of the high-brightness imaging
region.

5. The legged mobile robot according to claim 1, further including:a body
and a head, legs and arms connected to the body;and the brightness
reduction operation execution means drives the legs so as to reduce the
brightness of the high-brightness imaging region.

7. The legged mobile robot according to claim 6, further including:a body,
arms connected to the body, and hands connected to the arms, and the
high-brightness incidence direction determination operation execution
means determines the direction of the high-brightness incident light by
driving at least the hands.

8. A method of controlling a legged mobile robot having an imaging device
for taking an image utilizing incident light from external world in which
an object to be imaged is present, comprising the step of:determining
whether a high-brightness imaging region is present in the image taken by
the imaging device and executing brightness reduction operation to reduce
brightness of the high-brightness imaging region produced by
high-brightness incident light, when the high-brightness imaging region
is present in the image.

9. The method according to claim 8, wherein the robot includes a body,
arms connected to the body and hands connected to the arms;and the step
of determining drives at least one of the hands to block the
high-brightness incident light, thereby reducing the brightness of the
high-brightness imaging region.

10. The method according to claim 9, the object is a human being, and the
step of determining drives at least one of the hands to block the
high-brightness incident light while holding imaging parameters of the
human being.

11. The method according to claim 8, wherein the robot includes a body and
a head, which is connected to the body and equipped with the imaging
device;and the step of determining rotates the head so as to reduce the
brightness of the high-brightness imaging region.

12. The method according to claim 8, wherein the robot includes a body and
a head, legs and arms connected to the body;and the step of determining
drives the legs so as to reduce the brightness of the high-brightness
imaging region.

13. The method according to claim 8, further including the step
of:executing incidence direction determining operation for determining
direction of the high-brightness incident light of the high-brightness
imaging region.

14. The method according to claim 13, wherein the robot further includes a
body, arms connected to the body, and hands connected to the arms;and the
step of executing determines the direction of the high-brightness
incident light by driving at least the hands.

Description:

BACKGROUND OF THE INVENTION

[0001]1. Field of the Invention

[0002]This invention relates to a legged mobile robot, particularly to a
legged mobile robot equipped with a CCD camera (imaging device) that
serves as a visual sensor capable of imaging objects with appropriate
brightness even when the sun or other such bright light source falls
within the image.

[0003]2. Description of the Related Art

[0004]As set out in Japanese Laid-Open Patent Application No. 2006-129084,
for example, technologies have been developed for predicting the
location, shape and the like of a ghost formed on the imaging plane of an
imaging device by internal reflection when a bright light source like the
sun falls within the angle of view of a camera, determining which portion
of the taken image is the ghost, and correcting (reducing) the determined
ghost portion in response to photographer instructions or automatically.

SUMMARY OF THE INVENTION

[0005]Although the technology of the reference is intended for application
to a digital camera or video camera used to photograph a human being, a
camera of this type is also sometimes used as a visual sensor mounted on
a legged mobile robot or other mobile object.

[0006]In such a case, when a bright light source such as the sun or a
spotlight is imaged by the imaging device, the brightness of a human
being or other object to be imaged present at the portion affected by the
light source is, as shown in FIG. 16, blotted out, making it impossible
to identify the object. In FIG. 16, a human being actually present on the
right side of the image cannot be discerned.

[0007]The object of this invention is to overcome this problem and provide
a legged mobile robot that enables imaging of an object with suitable
brightness even when a bright light source such as the sun is visible to
the camera (imaging device) used.

[0008]In order to achieve the object, this invention provides a legged
mobile robot having an imaging device for taking an image utilizing
incident light from external world in which a human being to be imaged is
present, comprising: brightness reduction operation execution means for
determining whether a high-brightness imaging region is present in the
image taken by the imaging device and for executing brightness reduction
operation to reduce brightness of the high-brightness imaging region
produced by high-brightness incident light, when the high-brightness
imaging region is present in the image.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]The above and other objects and advantages of the invention will be
more apparent from the following description and drawings in which:

[0010]FIG. 1 is a front view of a legged mobile robot according to
embodiments of the invention;

[0011]FIG. 2 is a side view of the robot shown in FIG. 1;

[0012]FIG. 3 is an explanatory diagram showing a skeletonized view of the
robot shown in FIG. 1;

[0013]FIG. 4 is a block diagram showing the configuration of the robot
shown in FIG. 1 primarily with regard to input/output of an electronic
control unit (ECU);

[0020]FIG. 11 is a set of views for explaining the operation of FIG. 10;

[0021]FIG. 12 is a subroutine flowchart showing leg control 1 of FIG. 9;

[0022]FIG. 13 is a set of views for explaining the operation of FIG. 12;

[0023]FIG. 14 is a subroutine flowchart showing leg control 2 of FIG. 9;

[0024]FIG. 15 is a set of views for explaining the operation of FIG. 14;
and

[0025]FIG. 16 is a view showing an example of a sight that is planned to
be imaged by a camera (imaging device) according to the embodiments.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026]FIG. 1 is a front view of a legged mobile robot, i.e., a mobile
object according to a first embodiment of this invention is mounted. FIG.
2 is a side view of the robot shown in FIG. 1.

[0027]As shown in FIG. 1, the legged mobile robot (mobile object),
designated by the reference symbol 10 in the drawings and sometimes
referred to simply as "robot" hereinafter, is equipped with left and
right legs 12L, 12R. Here and hereinafter L and R are used to indicate
left and right. The legs 12L, 12R are connected to the bottom of a body
14. A head 16 is connected to the top of the body 14 and left and right
arms 20L, 20R are connected to opposite sides of the body 14. Hands (end
effectors) 22L, 22R are connected to the distal ends of the left and
right arms 20L, 20R. In this embodiment, the legged mobile robot is
exemplified by a humanoid robot that has two legs and two arms and stands
to a height of about 1.3 m.

[0028]As shown in FIG. 2, a storage unit 24 is mounted on the back of the
body 14. The storage unit 24 houses, inter alia, an Electronic Control
Unit (ECU) 26 and a battery (not shown).

[0029]FIG. 3 is an explanatory diagram showing a skeletonized view of the
robot 10 shown in FIG. 1. The internal structures of the robot 10 will be
explained with reference to this drawing, with primary focus on the
joints. Since the illustrated robot 10 is laterally symmetrical,
affixation of L and R will be omitted in the explanation of FIG. 3.

[0030]The left and right legs 12 are each equipped with a thigh link 30, a
shank link 32, and a foot member 34. The thigh link 30 is connected to
the body 14 through a hip (crotch) joint. The body 14 is shown
schematically in FIG. 3 as a body link 36. The body link 36 comprises an
upper section 36a and a lower section 36b connected through a joint 38 to
be movable relative to each other.

[0031]The thigh link 30 and shank link 32 are connected through a knee
joint. The shank link 32 and the foot 34 are connected through an ankle
joint. The hip joint comprises a rotary shaft 40 rotatable about a Z-axis
(yaw axis), a rotary shaft 42 rotatable about a Y-axis (pitch axis), and
rotary shaft 44 rotatable about an X-axis (roll axis). In other words,
the hip joint has three degrees of freedom.

[0032]The knee joint comprises a rotary shaft 46 rotatable about the
Y-axis and has one degree of freedom. The ankle joint comprises a rotary
shaft 48 rotatable about the Y-axis and a rotary shaft 50 rotatable about
the X-axis and has two degrees of freedom. Thus the left and right legs
12 are each imparted with 6 rotary shafts (degrees of freedom)
constituting 3 joints, so that the legs as a whole are imparted with 12
rotary shafts (degrees of freedom).

[0034]The left and right arms 20 are each equipped with an upper arm link
52 and a forearm link 54. The upper arm link 52 is connected to the body
14 through a shoulder joint. The upper arm link 52 and forearm link 54
are connected through an elbow joint, and the forearm link 54 and hand 22
are connected through a wrist joint.

[0035]The shoulder joint comprises a rotary shaft 56 rotatable about the
Y-axis, a rotary shaft 58 rotatable about the X-axis, and a rotary shaft
60 rotatable about the Z-axis. It has three degrees of freedom. The elbow
joint comprises a rotary shaft 62 rotatable about the Y-axis and has one
degree of freedom. The wrist joint comprises a rotary shaft 64 rotatable
about the Z-axis, a rotary shaft 66 rotatable about the Y-axis, and a
rotary shaft 68 rotatable about the X-axis. It has three degrees of
freedom. Thus the left and right arms 20 are each imparted with 7 rotary
shafts (degrees of freedom) constituting 3 joints, so that the arms as a
whole are imparted with 14 rotary shafts (degrees of freedom).

[0036]Like the legs 12, the arms 20 are also driven by actuators (not
shown). The arm actuators that drive the arms 20 comprise 14 electric
motors installed at appropriate locations on the body 14 and arms 20 to
drive the 14 rotary shafts independently. The legs 12 and arms 20 of the
robot 10 are imparted with desired movements by being controlled the
operation of the leg actuators and arm actuators to drive the rotary
shafts to suitable angles.

[0037]The hands 22 are each equipped with 5 fingers generally designated
by the reference symbol 70. The fingers 70 are drivable by hand actuators
(not shown) and can be operated in coordination with the arms 20 to grasp
objects, point in a suitable direction and execute other such operations.

[0038]The head 16 is connected to the body 14 through a neck joint that
comprises a rotary shaft 72 rotatable about the Z-axis and a rotary shaft
74 rotatable about the Y-axis. It has two degrees of freedom. The rotary
shafts 72 and 74 are individually driven by head actuators (not shown).
The head 16 can be faced in a desired direction by being controlled the
operation of the head actuators to drive the rotary shafts 72 and 74 to
suitable angles. The upper section 36a and lower section 36b can be
rotated relative to each other by driving an actuator (not shown)
installed at the joint 38.

[0039]A force sensor (six-axis force sensor) 76 attached to each of the
left and right legs 12 produces outputs or signals representing the floor
reaction force components Fx, Fy and Fz of three directions and the
moment components Mx, My and Mz of three directions acting on the leg 12
from the floor. A similar force sensor 78 attached to each of the left
and right arms 20 between the hand 22 and the wrist joint produces
outputs or signals representing the external force components Fx, Fy and
Fz of three directions and the moment components Mx, My and Mz of three
directions acting on the arm 20.

[0040]An inclination sensor 80 installed on the body 14 produces outputs
or signals representing state quantities of the body 14, including its
inclination angle and angular velocity relative to the vertical axis. Two
(left and right) imaging devices, specifically two CCD cameras
(hereinafter sometimes called simply "cameras") 82 are installed in the
head 16 for taking images utilizing incident light from the external
world (ambience) in which a human being or other object to be imaged is
present. A voice input/output device 84 comprising a microphone 84a and a
speaker 84b is also installed in the head 16.

[0041]The outputs of the sensors and the like are sent to the ECU 26
(shown in FIG. 2). The ECU 26 is constituted as a microcomputer
comprising a CPU, input/output circuits, ROM, RAM and other components,
none of which are shown in the drawings.

[0042]FIG. 4 is a block diagram showing the configuration of the robot 10
primarily with regard to input/output of the ECU 26.

[0043]As illustrated, the robot 10 is equipped not only with the aforesaid
sensors and the like but also with rotary encoders 86, a gyro-sensor 88,
a Global Positioning System (GPS) receiver 90, and an IC tag signal
receiver (reader) 94 wirelessly connected to an IC tag 92 carried (worn)
by a human being (object of imaging) for receiving Integrated Circuit
(IC) tag information transmitted by the IC tag 92.

[0044]The rotary encoders 86 produce outputs or signals indicative of the
rotation angles, i.e. joint angles, of the respective rotary shafts 40
and the like. The gyro-sensor 88 produces an output or signal indicative
of the direction and distance of movement of the robot 10. The GPS
receiver 90 receives radio signals transmitted from satellites, acquires
information on the position (latitude and longitude) of the robot 10, and
sends the position information to the ECU 26. The IC tag signal receiver
94 wirelessly receives and sends to the ECU 26 identification information
(RFID (Radio Frequency ID) information, specifically identification
information identifying the human being who is the wearer of the IC tag
92)) stored in and transmitted from the IC tag 92.

[0045]The ECU 26 controls walking by generating a gait based on the
outputs of the force sensors 76, inclination sensor 80, and rotary
encoders 86. Specifically, it makes the robot 10 move (walk) by
controlling the operation of leg actuators (designated 100) to drive the
legs 12. The gait generation and walking control is performed in
accordance with the teaching of Applicant's Japanese Patent No. 3726081
and will not be explained in detail here.

[0046]Concomitantly with the walking and other control, the ECU 26 further
controls the operation of the arm actuators (designated 102) and the hand
actuators (designated 104), thereby driving the arms 20 and hands 22, and
controls the operation of the head actuators (designated 106), thereby
regulating the orientation of the head 16.

[0047]In addition, the ECU 26 operates to conduct brightness reduction
when high-brightness imaging region is imaged by the camera 82.

[0048]FIG. 5 is a block diagram functionally illustrating the
configuration when the ECU 26 operates to conduct brightness reduction.

[0049]As can be seen, when the operations of the ECU 26 are viewed by that
function, the ECU comprises a stereo processor 26a, a histogram generator
26b, an exposure parameter setting unit 26c, an image processor 26d and a
behavior generator 26e.

[0050]The stereo processor 26a inputs the outputs of the two cameras
(imaging devices) 82 mounted on the mobile object (robot) 10 and adapted
to take images utilizing incident light from the external world in which
an object (of imaging), specifically a human being, is present. Upon
inputting the outputs, it performs stereo processing to calculate
distance information for each pixel from the parallax of the inputted
images. The number of pixels of the cameras 82 is 320×240. The
stereo processor 26a calculates and outputs three-dimensional (3D) data
from gray-scale image data.

[0051]The histogram generator 26b creates brightness histograms of the
taken images and weights them by distance or in accordance with distance.

[0052]The exposure parameter setting unit 26c defines an exposure
parameter (specifically, shutter speed) based on the brightness at the
distance desired to be imaged. Owing to the fact that the cameras 82 are
installed in the robot 10 to function as a visual sensor, the cameras 82
do not themselves seek out objects (of imaging) but are required to
extract objects (of imaging) from taken images. So the lenses of the
cameras 82 are fixed at the smallest aperture (the iris is set to the
minimum) and are adjusted to be in focus at a near distance, specifically
between about 0.5 m and 2.5 m. Therefore, only the shutter speed is
adjustable as an exposure parameter.

[0053]The image processor 26d is responsive to movement of the robot 10
for performing image processing as a visual sensor.

[0054]The behavior generator 26e generates a predetermined behavior of the
robot 10 for reducing a high-brightness imaging region, if present,
imaged therein due to high-brightness incident light such as a light
source.

[0055]The operation of the ECU 26 will now be explained in detail.

[0056]FIG. 6 is the former half of a flowchart that, like FIG. 5, shows
the processing performed by the ECU 26 for brightness reduction. The
latter half of the flowchart is shown in FIG. 7.

[0057]In S10, it is determined whether a human being (object of imaging)
is present. The presence/absence of a human being is determined from the
output of the IC tag signal receiver 94, which receives identifying
information transmitted by the IC tag 92 carried (worn) by the human
being.

[0058]When the result in S10 is NO, the aforesaid processing is repeated
and, when it is YES, the program goes to S12, in which the robot 10 moves
closer to the human being, to S14, in which it approaches to within a
predetermined distance of the human being, and to S16, in which it moves
still closer to the human being.

[0059]Next, in S18, it is checked whether the direction and position
(location) of a high-brightness imaging region in the image has been
detected (i.e., it is determined whether a high-brightness imaging region
is present in the image taken by the imaging device (CCD cameras 82)).
When the result is YES, the program goes to S20, in which the optimum
posture of the hand 22 is calculated, and when it is NO, the program goes
to S22, in which a default value (initial value) of the hand 22 is
adopted.

[0060]Next, in S24, the hand 22 is driven to hold it up to the light
source, e.g., the sun, more exactly up to the high-brightness imaging
region in the image. In other words, the hand 22 is driven to block
bright incident light from a light source or the like.

[0061]Next, in S26, the hand 22 is drawn nearer (toward the body 14),
whereafter the program goes to S28, in which it is checked whether the
hand 22 has become larger than the light source, more exactly the
high-brightness imaging region, in other words whether the
high-brightness incident light has been blocked. When the result is NO,
the program returns to S24 to repeat the aforesaid procedure.

[0062]FIG. 8 is a diagram for explaining the aforesaid operation of the
hand 22 for reducing the brightness of the high-brightness imaging
region.

[0063]As illustrated, the robot 10 moves the hand 22R to block or
intercept the high-brightness incident light (optical axis) from the
light source. The robot 10 brings the hand 22R nearer to the camera 82
mounted on its head 16 by moving it progressively through the positions A
and B to position C. As a result, the blocked area of the incident light
from the light source increases but the probability of the imaging region
for the person being blocked also increases.

[0064]In the processing of S18 to S28, therefore, the hand 22 is driven to
a position where the high-brightness incident light from the light source
is totally blocked, i.e., to position as close to A as possible, while
holding or maintaining the imaging region for the human being, in other
words, while holding or maintaining the imaging parameters for the human
being.

[0065]The explanation of FIG. 6 will be continued.

[0066]Next, in S30, the exposure parameter of the human being, i.e., the
shutter speed, is calculated, whereafter, in S32, the possibility of
extracting the human being's face from the image is determined.

[0067]Next, in S34, it is checked whether it is impossible to extract the
face. When the result is YES, the program goes to S36, in which it is
checked whether the high-brightness incident light from the light source
or the like has caused the maximum value of the imaged brightness of the
high-brightness imaging region to exceed the brightness of the face. When
the result is YES, the program goes to S38, in which the amount of
rotation of the head 16 is calculated.

[0068]Next, in S40, the direction and distance the head 16 needs to be
moved to avoid the high-brightness incident light from the light source
or the like is calculated, whereafter, in S42, a command value for moving
the head 16 in that direction is calculated. The program then goes to
S44, in which the head 16 is moved (rotated) accordingly, and to S46, in
which limit processing is performed.

[0069]Thus, when it is found that the driving of the hand 22 in S18 to S28
does not enable the brightness of the high-brightness imaging region to
be thoroughly reduced, the head 16 is rotated to avoid the
high-brightness incident light.

[0070]The program then goes to S48, in which face extraction processing is
performed, and to S50, in which it is checked whether the extraction of
the face was achieved. When the result in S50 is NO, the program goes to
S52 (FIG. 7), in which it is checked whether the average value of the
brightness of the high-brightness imaging region exceeds the brightness
of the extracted face. When the result in S52 is YES, the program goes to
S54, in which an amount of gait (turning etc.) correction is calculated.
When the result in S52 is NO, S54 is skipped.

[0071]Next, in S56, a gait command value is determined based on the
calculated correction amount and is outputted, whereafter, in S58, the
legs 12 are driven to implement walking control. The program then returns
to S18 to repeat the aforesaid processing. In the aforesaid processing,
the result in S34 being NO or the result in S50 being YES means that face
extraction was achieved, so the remaining processing steps are skipped.

[0072]As set out in the foregoing, the first embodiment is configured to
have a legged mobile robot (10) having an imaging device (CCD camera 82)
for taking an image utilizing incident light from external world in which
a human being to be imaged is present, comprising: brightness reduction
operation execution means (the ECU 26, stereo processor 26a, histogram
generator 26b, exposure parameter setting unit 26c, image processor 26d,
behavior generator 26e, S10 to S58) for determining whether a
high-brightness imaging region is present in the image taken by the
imaging device and for executing brightness reduction operation to reduce
brightness of the high-brightness imaging region produced by
high-brightness incident light, when the high-brightness imaging region
is present in the image. Owing to this configuration, when the imaged
high-brightness imaging region is present owing to high-brightness
incident light from the sun or the like, the legged mobile robot 10 can
reduce the brightness to image a human being or other object with
suitable brightness.

[0073]The legged mobile robot (10) is configured to comprise at least a
body (14), arms (20) connected to the body and hands (22) connected to
the arms (20) and the brightness reduction operation execution means
drives at least one of the hands (22) to block the high-brightness
incident light, thereby reducing the brightness of the high-brightness
imaging region (S18 to S28). With this, the legged mobile robot 10 having
the aforesaid effects further enables a human being or other object to be
imaged with suitable brightness without enhancing the performance of the
imaging device or the image processing.

[0074]In the legged mobile robot 10, the object (of imaging) is a human
being and the brightness reduction operation execution means drives at
least one of the hands (22) to block high-brightness incident light while
holding the imaging region of the human being, i.e., imaging parameters
of the human being (S18 to S28). With this, the legged mobile robot (10)
having the aforesaid effects further enables reliable imaging of a human
being who is the object (of imaging).

[0075]The legged mobile robot (10) is further configured to comprise at
least a body (14) and a head (16), which is connected to the body (14)
and equipped with the imaging device, and the brightness reduction
operation execution means rotates the head (16) so as reduce the
brightness of the high-brightness imaging region (S36 to S46). In this
aspect also, therefore, the legged mobile robot 10 enables a human being
or other object to be imaged with suitable brightness without enhancing
the performance of the imaging device or the image processing, and
further enables reliable imaging of an object even when the
high-brightness imaging region is relatively large.

[0076]The legged mobile robot (10) is further configured to comprise at
least a body (14) and a head (16), legs (12) and arms (20) connected to
the body (14), and the brightness reduction operation execution means
drives the legs (12) so as to reduce the brightness of the
high-brightness imaging region (S54 to S58). In this aspect also,
therefore, the legged mobile robot 10 enables a human being or other
object to be imaged with suitable brightness without enhancing the
performance of the imaging device or the image processing, and further
enables still more reliable imaging of an object even when the
high-brightness imaging region is relatively large.

[0077]FIG. 9 is a flowchart that, similar to FIG. 6, but shows the
operation of the legged mobile robot according to a second embodiment of
this invention.

[0078]Explaining this, in S100, it is checked whether the image taken
utilizing incident light from the external world (ambience) in which the
object to be imaged (human being) is present includes (or has not been
removed of) the high-brightness imaging region produced by the
high-brightness incident light.

[0079]When the result in S100 is NO, the remaining process steps are
skipped. When it is YES, the program goes to S102, in which it is checked
whether the direction of the high-brightness imaging region has been
determined or identified, in other words, whether the direction of the
high-brightness incident light has been determined. When the result in
S102 is NO, the program goes to S104, in which an incidence direction
determining operation for determining the direction of the
high-brightness incident light is performed.

[0080]FIG. 10 is a flowchart showing this operation. FIG. 11 is a set of
views for explaining the operation of FIG. 10. In the following,
explanation will be made in accordance with FIG. 10, with occasional
reference to FIG. 11.

[0081]In S200, the hands 22 are driven to restrict the view angle in a
desired direction. Specifically, as shown in FIG. 11A, since the
direction of the incident light is unknown, the direction in which the
object (of imaging) is present is made a target toward which both the
left and right hands 22R, 22L are driven. At this time, a space is left
between the hands 22R, 22L and the driving is performed so as not to
block the incident light from the object (of imaging).

[0082]Next, in S202, as shown in FIG. 11B and FIG. 11C, the head 16, body
14 and hands 22 are driven leftward away from the object (of imaging)
with the space between the hands 22R, 22L maintained, until the
high-brightness imaging region is eliminated from the image. In this
operation, once the motion of the body 14 and legs 12 reach their
permissible limits, the head 16 and hands 22 are driven further leftward
to the maximum value of leftward movability Almax.

[0083]When the high-brightness imaging region has been eliminated from the
image, the program goes to S204, in which the direction at that time,
i.e., the high-brightness incident light direction, is recorded as Al.

[0084]Next, in S206, the head 16, body 14 and hands 22 are returned in the
desired direction, i.e., they are driven to the posture mentioned
regarding S200.

[0085]Next, in S208, a reverse operation is performed in which the head
16, body 14 and hands 22 are driven rightward away from the object (of
imaging) with the space between the hands 22R, 22L maintained, until the
high-brightness imaging region is eliminated from the image. When the
high-brightness imaging region has been eliminated from the image, the
program goes to S210, in which the direction at that time, i.e., the
high-brightness incident light direction, is recorded as Ar. The incident
light directions designate angles in the plane of FIG. 11.

[0086]Next, in S212, driving is performed to return the head 16 and body
14 to the center (front) and lower the hands 22.

[0087]Next, in S214, it is checked whether Al and Ar were acquired
(whether the direction of the high-brightness incident light was
determined). When it is found that Al and Ar were acquired, the program
goes to S216, in which the two values are divided by 2 and determination
of the incident light direction is deemed successful. When one of them
was not acquired, the program goes to S218, in which determination is
deemed to have failed.

[0088]Explanation of the flowchart of FIG. 9 will be continued.

[0089]Next, in S106, it is checked whether the incident light direction
was determined by the processing of FIG. 10. When the result is YES, the
program goes to S108, in which leg control 1 is performed.

[0090]FIG. 12 is a flowchart showing this operation. FIG. 13 is a set of
diagrams for explaining the operation of FIG. 12. In the following,
explanation will be made in accordance with FIG. 12, with occasional
reference to FIG. 13.

[0091]In S300, the desired position of each leg 12 is defined based on the
determined direction of the high-brightness incident light (the direction
of the high-brightness imaging region) and the position of the object (of
imaging). Next, in S302, the legs 12 and other members are driven to
commence walking and reach the destination in S304, whereupon the
operation is terminated.

[0092]Specifically, when the light source (high brightness) is within the
angle of view as shown in FIG. 13A, the legs 12 are, as shown in FIG.
13B, driven to move one step right while turning left, so as to avoid the
incident light (make the incident light fall outside the angle of view).

[0093]Explanation of the flowchart of FIG. 9 will be resumed.

[0094]After the processing in S108, the program returns to S102, and when
the result in S106 is NO (it is found that the incident light direction
was not determined), the program goes to S110, in which leg control 2 is
performed.

[0095]FIG. 14 is a flowchart showing this operation. FIG. 15 is a set of
views for explaining the operation of FIG. 14. Explanation will be made
in accordance with FIG. 14, with occasional reference to FIG. 15.

[0096]In S400, it is checked whether the high-brightness incident light
direction Al or Ar was acquired. When the result is YES, the program goes
to S402, in which the camera 82 is pointed to Al+(Ac/2) or, if Al is not
determined, the camera 82 is pointed to Ar+(Ac/2). As shown in FIG. 15A,
Ac indicates the angle of view. Thus, the aforesaid processing is
intended to keep the high-brightness incident light from entering the
angle of view.

[0097]When the result in S400 is NO, the program goes to S404, in which
the camera 82 is pointed to Almax+(Ac/2) or Armax+(Ac/2). Armax is the
maximum value of rightward movability. This processing is also intended
to keep the high-brightness incident light from entering the angle of
view.

[0098]Next, in S406, the direction of the camera 82 is changed or shifted.
Specifically, when the camera 82 was pointed left (right) in S402 or
S404, its direction is shifted right (left) in S406.

[0099]As shown in FIG. 15A to FIG. 15C, the aforesaid processing is
repeated until the high-brightness imaging region has been removed. Once
removal has been achieved, the program goes to S408, in which the walking
destination is defined at a position where the object (of imaging) is
seen at the center (front) with the direction of the camera 82 kept the
same, to S410, in which walking toward the destination is started, and
S412, in which the walking is stopped when it is determined that the
destination has been reached.

[0100]The explanation of the flowchart of FIG. 9 will be continued.

[0101]Following the processing in S110, the program returns to S102. When
the result in S102 is YES, the program goes to S112, in which the
position to which one of the hands 22 is to be extended is determined
based on the position of the object (of imaging) and the direction of the
high-brightness incident light, to S114, in which it is checked whether
the hand 22 at that position can hide the object (of imaging), and when
the result is YES, to S116, in which the hand 22 is driven in the manner
of S24 to S26 in the first embodiment.

[0102]In S116, therefore, the hand 22 can be driven to a position where
the high-brightness incident light from the light source is totally
blocked without blocking the incident light from the object (of imaging),
namely, to a position as near A as possible.

[0103]Next, in S118, it is checked whether the object (of imaging) is
imaged with suitable brightness. If the result is YES, the processing is
terminated. If it is NO, the program goes to S120, in which, as shown in
FIG. 8, the distance of the hand 22 from the image (in other words, from
the head 16) is changed and the aforesaid processing is repeated until it
is found that the distance limit (C in FIG. 8) has been reached. When it
is found in S122 that the distance limit has been reached, the program
goes to S108.

[0104]When the result in S114 is NO, the program goes to S124, in which
the width of the high-brightness imaging region that can be hidden is
determined. When it is found to be large, the program goes to S108. When
it is small, the program goes to S126, in which body control is
performed. This is control for driving the head 16 to move (avoid) the
high-brightness incident light. The program then goes to S102 to repeat
the aforesaid processing.

[0105]The second embodiment is thus configured to have a legged mobile
robot (10) having an imaging device (CCD camera 82) for taking an image
utilizing incident light from external world in which a human being to be
imaged is present, comprising: brightness reduction operation execution
means (the ECU 26, stereo processor 26a, histogram generator 26b,
exposure parameter setting unit 26c, image processor 26d, behavior
generator 26e, S10 to S58) for determining whether a high-brightness
imaging region is present in the image taken by the imaging device and
for executing brightness reduction operation to reduce brightness of the
high-brightness imaging region produced by high-brightness incident
light, when the high-brightness imaging region is present in the image;
and high-brightness incidence direction determination operation execution
means (the ECU 26, stereo processor 26a, histogram generator 26b,
exposure parameter setting unit 26c, image processor 26d, behavior
generator 26e, S100 to S104, S200 to S218) for executing incidence
direction determining operation for determining direction of the
high-brightness incident light of the high-brightness imaging region.
With this, when a bright light source such as the sun is visible to the
mounted camera (imaging device) 82, the incidence direction of the high
brightness can be determined, so that it can be avoided while correcting
the camera parameters to image the object (of imaging) with suitable
brightness.

[0106]The legged mobile robot (10) is configured to comprise at least a
body (14), arms (20) connected to the body (14), and hands (22) connected
to the arms (20), and the high-brightness incidence direction
determination operation execution means determines the direction of the
high-brightness incident light by driving at least the hands (S104, S200
to S218, S106). With this, the robot 10 having the aforesaid effects can
further readily determine the incidence direction of the high brightness.

[0107]The robot 10 further comprises the brightness reduction operation
execution means for executing the brightness reduction operation for
reducing the brightness of the high-brightness imaging region (S108,
S110, S300 to S304, S400 to S412, S116 to S126). With this, the robot 10
having the aforesaid effects is further responsive to the presence of an
imaged high-brightness imaging region caused by high-brightness incident
light from the sun or the like for reducing the brightness to enable a
human being or other object to be imaged with suitable brightness.

[0108]The legged mobile robot (10) comprises at least a body (14), arms
(20) connected to the body (14), and hands (22) connected to the arms
(20), and the brightness reduction operation execution means drives at
least one of the hands 22 to block the high-brightness incident light,
thereby reducing the brightness of the high-brightness imaging region
(S116 to S122). Therefore, the robot 10 having the aforesaid effects
further enables a human being or other object to be imaged with suitable
brightness without enhancing the performance of the imaging device or the
image processing.

[0109]The robot (10) is further configured to comprise at least a body
(14) and a head (16) connected to the body (14) and equipped with the
imaging device, and the brightness reduction operation execution means to
rotate the head (16) so as to avoid the high-brightness incident light
(S126). In this aspect also, therefore, the legged mobile robot 10
enables a human being or other object to be imaged with suitable
brightness without enhancing the performance of the imaging device or the
image processing, and further enables reliable imaging of an object even
when the high-brightness imaging region is relatively large.

[0110]The legged mobile robot (10) is further configured to comprise at
least a body (14) and a head (16), legs (12) and arms (20) connected to
the body (14), and the brightness reduction operation execution means
drives the legs (12) so as to avoid the high-brightness incident light
(S108, S300 to S304, S110, S400 to S412). In this aspect also, therefore,
the legged mobile robot 10 enables a human being or other object to be
imaged with suitable brightness without enhancing the performance of the
imaging device or the image processing, and further enables still more
reliable imaging of an object even when the high-brightness imaging
region is relatively large.

[0111]In the foregoing explanation, the object (of imaging) was presumed
to be a human being but it can instead be some other object, such as a
tool or workpiece, associated with the task performed by the robot 10.

[0112]In the aforesaid configurations, the presence/absence of an object
(of imaging) is determined from the output of the IC tag signal receiver
94, which receives identifying information transmitted by the IC tag 92
carried (worn) by the object (of imaging). However, the determination can
instead be made from the output of the camera 82. Alternatively, the
robot 10 can be informed of the presence/absence of an object (of
imaging) by inputting a command from the outside.

[0113]In the foregoing explanation, a legged mobile robot, specifically a
biped walking robot, was taken as an example of the mobile object.
However, this is not a limitation and the mobile object can be of any
kind capable of moving autonomously.

[0114]Japanese Patent Application Nos. 2007-224755 and 2007-224756 both
filed on Aug. 30, 2007, are incorporated herein in its entirety.

[0115]While the invention has thus been shown and described with reference
to specific embodiments, it should be noted that the invention is in no
way limited to the details of the described arrangements; changes and
modifications may be made without departing from the scope of the
appended claims.